The present invention relates to a device making it possible to maintain a liquid in a substantially horizontally axed duct and having an open outlet end, when the outflow of said liquid is stopped or when its flow drops below a given threshold.
In a substantially horizontal duct, whose outlet end issues into a gaseous medium such as water vapor or steam, or significant drop in the flow has the effect of gas entering the pipe system. When the flow of liquid in the pipe system rises to its normal operating level, the gas present therein leads to water hammer.
Moreover, the temperature of the liquid circulating in the duct may suddenly drop and this phenomenon is accompanied by a drop in the flow. As a result of the density effects between the cold liquid and the hot liquid, a stratification of said liquid then occurs and advances along the pipe system, so that severe thermal stresses can be produced in this way.
Situations of this type can occur in pressurized water nuclear reactors, equipped with steam generators of a particular type. Thus, in certain steam generators, like that described in FR-A-No. 2 428 787, the feed water of the water - steam circuit of the reactor is admitted into the generator by a horizontal duct issuing into a toroidal collector having orifices along its lower generatrix. This collector is placed in the steam atmosphere prevailing in the upper part of the generator, so that water hammer can occur as a result of the steam entering the horizontal duct when there is a significant drop in the flow in the water - steam circuit.
Moreover, under certain operating conditions, the temperature of the feed water injected into the steam generator can be reduced and so can the flow. It is then possible for the aforementioned stratification phenomenon to occur, leading to severe thermal stresses on the connecting pipe between the envelope of the generator and the feed water intake duct.